U.S. patent number 4,655,316 [Application Number 06/711,549] was granted by the patent office on 1987-04-07 for acoustic diaphragm.
This patent grant is currently assigned to JBL Incorporated. Invention is credited to Fancher M. Murray.
United States Patent |
4,655,316 |
Murray |
April 7, 1987 |
Acoustic diaphragm
Abstract
An acoustic diaphragm is made of metallic sheet material forming
a raised pattern of the material and unraised sectors of the
material. The diaphragm is of the dome-shaped variety. The raised
pattern incorporates sets of raised strip elements. There is a set
of such elements extending radially from the vicinity of the apex.
There is a set extending along areas of the sheet material between
the radially extending elements, this second set including pairs of
strip elements which intersect one another along such areas. There
is also a set of circumferentially extending raised strip elements.
The form of the radially extending elements changes along their
lengths; for example, they rise to levels which vary along their
lengths.
Inventors: |
Murray; Fancher M. (Thousand
Oaks, CA) |
Assignee: |
JBL Incorporated (Northridge,
CA)
|
Family
ID: |
24858529 |
Appl.
No.: |
06/711,549 |
Filed: |
March 13, 1985 |
Current U.S.
Class: |
181/164; 181/168;
181/173 |
Current CPC
Class: |
H04R
1/023 (20130101); G10K 13/00 (20130101) |
Current International
Class: |
G10K
13/00 (20060101); H04R 1/02 (20060101); G01K
013/00 () |
Field of
Search: |
;181/164,168,157,172-174 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Fuller; Benjamin R.
Attorney, Agent or Firm: Marks Murase & White
Claims
What is claimed is:
1. An acoustic diaphragm, comprising:
metallic sheet material having a raised pattern formed thereon;
said raised pattern including a plurality of first raised strip
elements extending radially from a point on said matallic sheet
material and a plurality of second raised strip elements;
said second raised strip elements including a plurality of pairs of
intersecting strip elements, each of said intersecting pairs being
positioned between adjacent first raised strip elements.
2. An acoustic diaphragm as defined in claim 1 wherein said sheet
material has substantially a dome shape.
3. An acoustic diaphragm as defined in claim 1 wherein said sheet
material is shaped to have an apex and wherein said first raised
strip elements extend radially from the vicinity of said apex.
4. An acoustic diaphragm as defined in claim 1 wherein said raised
pattern further comprises a plurality of third raised strip
elements, said third raised strip elements extending
circumferentially about said metallic sheet material and
intersecting said first raised strip elements.
5. An acoustic diaphragm as defined in claim 1 wherein said
metallic sheet material defines a surface and said first raised
strip elements have a length extending along said surface, and
wherein said first raised strip elements have rise levels extending
above said surfaces which vary along said length of said first
raised strip elements.
6. An acoustic diaphragm as defined in claim 1 wherein said first
raised strip elements extend along a length of said material and
have base widths which vary along said length.
7. An acoustic diaphragm as defined in claim 1 wherein said first
raised strip elements are substantially semi-circular in
cross-section.
8. An acoustic diaphragm as defined in claim 1 wherein said
metallic sheet material defines a surface and said first raised
strip elements have rise levels extending above said surface, said
rise levels being substantially defined by an imaginary envelope
having the shape of a section of a spherical surface.
9. An acoustic diaphragm as defined in claim 1 wherein said sheet
material defines a substantially a dome-shaped surface, and wherein
said first raised strip elements have rise levels extending above
said surface which substantially define an imaginary envelope
having the shape of a section of a spherical surface.
10. An acoustic diaphragm as defined in claim 9 wherein said
spherical surfaces have different centers.
11. An acoustic diaphragm, comprising:
metallic sheet material having a raised pattern formed thereon;
said raised pattern including a plurality of first raised strip
elements extending radially from a point on said metallic sheet
material and a plurality of second raised strip elements interposed
between adjacent ones of said first raised strip elements and
extending at an angle with respect to said first raised strip
elements.
12. An acoustic diaphragm as defined in claim 11 wherein said
second raised strip elements are substantially straight.
13. An acoustic diaphragm as defined in claim 11 wherein said sheet
material has substantially a dome shape.
14. An acoustic diaphragm as defined in claim 11 wherein said sheet
material has an apex.
15. An acoustic diaphragm as defined in claim 14 wherein said first
raised strip elements extend radially from the vicinity of said
apex.
16. An acoustic diaphragm, comprising:
metallic sheet material having a raised pattern formed thereon;
said raised pattern including a plurality of first raised strip
elements extending radially from a point on said metallic sheet
material and at least two second raised strip elements extending
circumferentially about said metallic sheet material and
intersecting said first raised strip elements.
17. An acoustic diaphragm as defined in claim 16 wherein said
raised pattern further comprises a plurality of third raised strip
elements interposed between ones of said first raised strip
elements.
18. An acoustic diaphragm as defined in claim 16 wherein said sheet
material has substantially a dome shape.
19. An acoustic diaphragm as defined in claim 16 wherein said sheet
material has an apex.
20. An acoustic diaphragm as defined in claim 19 wherein said first
raised strip elements extend radially from the vicinity of said
apex.
21. An acoustic diaphragm, comprising:
sheet material formed into an arcuate three-dimensional surface
having a substantially round base, said surface having a raised
pattern formed thereon and said base having a maximum dimension of
not greater than approximately ten inches;
said raised pattern including plurality of first raised strip
elements extending radially from a point on said sheet material and
second raised strip elements interposed between adjacent ones of
said first raised strip elements and extending at an angle with
respect to said first raised strip elements.
22. An acoustic diaphragm as defined in claim 21 wherein said
second raised strip elements are substantially straight.
23. An acoustic diaphragm as defined in claim 21 wherein said base
is substantially circular and has a diameter not greater than
approximately ten inches.
24. An acoustic diaphragm as defined in claim 21 wherein said
surface is shaped to have an apex and wherein said first raised
strip elements extend radially from the vicinity of said apex.
25. An acoustic diaphragm as defined in claim 21 wherein said first
raised strip elements extend along a length of said surface and
have rise levels extending above said surface, said rise levels
varying along said length.
26. An acoustic diaphragm as defined in claim 21 wherein said
surface defines substantially a dome shape, and said first raised
strip elements have rise levels extending above said surface
substantially defined by an imaginary envelope having the shape of
a section of a spherical surface.
Description
FIELD OF THE INVENTION
The invention pertains to the field of acoustic diaphragms.
BACKGROUND OF THE INVENTION
Acoustic diaphragms of soft material, such as paper or composites
of a soft material and phenolic, have been most commonly adopted.
The softness tends to damp out local area oscillations along the
material which tend to have a negative effect on the frequency
response of the diaphragm. Also, because of its softness, the
material itself does not generate a sound as a result of the
movement of its structure in connection with such local area
oscillations.
The strength and stiffness requirements of diaphragms, and the
relatively lesser degree of strength of paper or other soft
materials, typically leads to relatively larger masses for
diaphragms made of such materials. Since there generally is a
mass-related frequency response roll-off at the upper frequency end
for a diaphragm, this mass factor typically results in a roll-off
in the frequency response at a significantly lower frequency than
would otherwise be achieved.
For example, paper diaphragms which are used for frequencies from
about 5 kilohertz to about 20 kilohertz (the upper part of the
audio range for humans) typically have responses which roll-off
significantly below the 20 kilohertz point.
Much effort has gone into attempting to improve various forms of
paper or other soft diaphragms. Thus, relatively strong paper
diaphragms of less than typical mass have been made. By way of
example, in cone-shaped diaphragms of relatively large size, thus
particularly adapted for the lower end of the audio spectrum,
ridges have been provided to increase effectiveness. The usefulness
and role of such in cone-shaped paper diaphragms having base
diameters as small as about 12 inches (30.5 centimeters) has been
significantly recognized.
Hard diaphragms of metallic material, for example having a dome
shape, have been used to a generally lesser extent than soft
diaphragms. Metal can typically provide more strength for the same
mass than paper or other soft material. Thus, metallic material is
advantageous with regard to roll-off at the high frequency end of a
diaphragm's response.
However, metal diaphragms are recognized as presenting practical
problems in formation for manufacturing purposes. For example, the
thin metal tends to break during formation in a cold die, and such
tendency can only be enhanced by complexity in the form of the
structure. Formation in a hot die overcomes this, but does
incorporate additional expense in constructing the hot die and also
brings some negative safety considerations into the manufacturing
process.
In addition, metallic diaphragms do not incorporate the damping
out, by the material, of local area oscillations, as occurs for
paper or other soft materials. The structural oscillations of the
metal as a result of such local area oscillations, most
particularly where the oscillations are resonances, also have a
negative impact on the sound generated by metallic diaphragms.
Specifically, "chirps" stemming from these relatively low level
localized resonances, result from the hard, unyielding nature of
the material, and interfere with the performance of such
diaphragms, particularly in respect to people with acute
hearing.
The present invention combines significant advantages typically
associated with hard as well as soft material diaphragms. In so
combining such advantages, it is most directly of concern with
reference to diaphragms of relatively small and intermediate
size.
SUMMARY OF THE INVENTION
In accordance with the invention, an acoustic diaphragm
incorporates metallic sheet material forming a raised pattern of
the material and unraised sectors of the material.
In accordance with other aspects of the invention, an acoustic
diaphragm incorporates sheet material forming a raised pattern of
the material and unraised sectors of the material, shaped to have
base dimensions of less than or equal to approximately ten
inches.
In an embodiment, in accordance with more detailed features of the
invention, the sheet material has substantially a dome shape and
the raised pattern of such material incorporates sets of raised
strip elements.
One set is a set of strip elements extending radially from the
vicinity of the apex of the sheet material. There is then a second
set of raised strip elements extending along areas of the sheet
material between the strip elements of the first set. This second
set of strip elements includes pairs which intersect one another
along such areas. There is also a third set of raised
circumferentially extending strip elements which intersect the
radially extending strip elements.
The radially extending raised strip elements of the first set have
rise levels which are substantially defined by an imaginary
envelope having the shape of a section of a spherical surface.
Relating to this, the unraised sheet material sectors lie
substantially along an imaginary spherical envelope surface having
a different center than for the surface applicable to the rise
levels of the radial strip elements.
The radial strip elements of the first set of strip elements
further have rise levels which change along their lengths, have
base widths which change along their lengths and, also, have
cross-section shapes which include substantially circular
sections.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view showing a diaphragm in accordance
with the invention joined with a voice coil assembly.
FIG. 2 is a front elevational view showing the diaphragm of FIG. 1,
along with its associated annular suspension construction and
annular skirt.
FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG.
2, shown somewhat schematically for purposes of clarity.
FIG. 4 is a cross-sectional view of a strip element taken along the
line 4--4 of FIG. 2.
FIG. 5 is a cross-sectional view of a strip element taken along the
line 5--5 of FIG. 2.
DETAILED DESCRIPTION
Referring, first, to FIG. 2, there is shown an acoustic diaphragm
12 along with its suspension or surround 14 and mounting skirt 16.
The diaphragm, surround and mounting skirt are a single piece of
thin metallic sheet material, advantageously and conveniently made
of titanium metal.
The form of the suspension 14, which essentially folds and unfolds
as the diaphragm moves back and forth, and of the skirt, are well
known and do not form a part of the present invention.
The diaphragm 12 incorporates a raised pattern 20 of the sheet
material and unraised sectors 22 generally between the elements of
the raised pattern (FIG. 1).
The diaphragm is of the dome-shaped variety--i.e., it generally
follows the shape of a spherical surface. In the embodiment shown,
there are ten radial strip elements 23 in the raised pattern (FIG.
1) having arcs of 36.degree. therebetween, as represented by the
arc 24 shown in FIG. 2. The raised pattern also incorporates an
inner circumferential strip element 26 and an outer circumferential
strip element 28, each intersecting each of the radial strip
elements. There is, then, also, a set of cross-strip elements 30.
There are a total of twenty such cross-strip elements consisting of
ten pairs. The strips of each pair extend across an area 32 between
adjacent radial strip elements and between the inner and outer
circumferential strip elements 26 and 28; and they intersect one
another along such area.
FIGS. 3-5 reveal some additional features of the diaphragm and its
raised pattern. However, before turning to a consideration of the
diaphragm and its raised pattern in additional detail, it will be
useful to additionally refer to the general accompanying context
for a diaphragm such as the one shown here, as revealed in FIGS. 1
and 2.
The diaphragm, of course, oscillates, generally in piston-like
fashion, in response to electrical signals in order to convert the
electrical signals into acoustic signals (sound). In FIG. 1, the
diaphragm 12 (with its suspension and skirt) is shown joined, in
typical fashion, to a coil form or bobbin 34 on which a voice coil
36, which carries the electrical signal, is wound. The bobbin is
adhered to the sheet material of the diaphragm 12, suspension 14
and skirt 16 generally along the circumferential line where the
diaphragm and suspension come together. Leads 40 to and from the
voice coil, for the voice coil signal, are provided. The skirt 16
typically is used to mount the diaphragm, suspension and skirt in
conventional fashion in a frame therefor (not shown).
Of course, in conventional fashion, the whole assembly, including
the voice coil, is typically mounted so that the voice coil is
immersed in a magnetic field. Then the electrical signals through
the voice coil, as a result of the magnetic field, exert forces on
the voice coil causing the diaphragm 12 to move back and forth,
with the changing signals, generating the acoustic (sound)
waves.
The suspension 14 expands and contracts (by folding and unfolding)
in order to accommodate the movement of the diaphragm. The
suspension shown is of the type described in U.S. Pat. No.
4,324,312, issued Apr. 13, 1982, titled Diaphragm Suspension
Construction. The suspension has pyramid-like structures 46
therealong (here twenty in number to go with the ten radial strip
elements), as described in such patent. The lines along the
suspension, shown in FIG. 2, are the fold lines for the suspension
structure. As described in such patent, the pyramid-like structures
rise above and below a suspension plane defined, with the
suspension in its quiescent, folded position, by an inner 48 and an
outer 50 circumferential fold line. A central fold line 52, which
is also circumferential, rises and falls along the pyramid-like
structures. As is apparent and previously indicated, FIG. 2 is
drawn to clearly show the suspension fold lines.
It is again emphasized that the particular form of the suspension
and of the skirt form no part of the present invention. However,
the form of suspension generally has been found to be particularly
desirable and advantageous and, as in other contexts, is considered
to be desirable and advantageous in the present context.
Referring to FIG. 2, the radial strip elements 23, which, of
course, are alike apart from their differing angular positions,
extend from the vicinity of the apex 53 of the diaphragm 12. The
radial strip elements 23, as is shown, merge together to form a
raised central portion 54 in such vicinity of the apex.
FIG. 3 is a generally cross-sectional view taken along the line
3--3 of FIG. 2. However, it is shown somewhat schematically in
order to more clearly reveal the form and structure of the
diaphragm. Thus, it shows the cross-sectional shape of the "north"
radial strip element 56 of FIG. 2, at the apex of the diaphragm,
without the remainder of the raised central portion 54 relating to
the other strip elements, in order to more clearly reveal the form
of the radial strips. It, of course, also shows the inner 26 and
outer 28 raised circumferential strip elements, so as to reveal
their form and shape. In addition, the drawing clearly shows, as
the background for the cross-sectional view, the "east-northeast"
60 and "west-northwest" 62 radial strip elements.
Referring to FIGS. 1, 2 and 3, the unraised sectors 22 of the
diaphragm, at their outer surfaces 64, lie along or follow an
imaginary spherical envelope surface. The envelope surface, then,
of course, coincides with the outer surface of the unraised
portions as shown at 64 in FIG. 3. The continuation of such
envelope surface is indicated beyond the outer edge of the
diaphragm by the unraised sector dash-dot lines 66 of FIG. 3. The
radius is indicated by the radial arrow 68 for the unraised sector
spherical surface in FIG. 3, and the center for such spherical
surface is indicated at 70.
Referring to FIG. 5, the rise level for the raised pattern at a
given position is the maximum level, above the immediately
surrounding unraised portion, to which the raised pattern rises.
Such rise level is illustrated for the north radial strip element
56, at the cross-section taken along the line 5--5 of FIG. 2, in
FIG. 5. Specifically, it is represented by radial element rise
level arrows 72 in FIG. 5. Thus, the outer surface of the radial
strip element, at the position of the cross-section, rises the
distance indicated by the arrows above the outer surface of the
surrounding unraised sectors.
Similarly, the base width for a part of the raised pattern at a
given position is the width across the outer surface of the raised
part, at the position, where such surface joins the surrounding
unraised sectors. Thus, at the position of the cross-section taken
along the line 5--5 of FIG. 2, the base width for the north radial
strip element is indicated by the radial element base width arrows
74 of FIG. 5.
Referring to FIGS. 2, 3 and 5, it is apparent from such figures,
that the rise level along each of the like radial strip elements
decreases as the strip element approaches the circumferential edge
of the diaphragm, at which point the element essentially ends, thus
returning to the unraised sector level. As is apparent by reference
to these figures, particularly FIG. 3, the levels to which the
radial strip elements rise, are also defined by an imaginary
spherical envelope surface. Such envelope coincides with and is
indicated by the top lines 76 and 80 for the east-northeast 60 and
west-northwest 62 radial strip elements in FIG. 3. The radius for
this spherical surface is indicated by the radial arrow 82 for the
radial element rise level spherical surface, in FIG. 3. The center,
then, is indicated at 84. The continuation of this spherical
surface beyond the outer edges of the diaphragm is represented by
the raised spherical surface dash-dot lines 86 in FIG. 3.
Beyond the fact that the radii for the unraised and raised
spherical surfaces are different, their centers, although of course
positioned along the same line (vertically down from the apex in
FIG. 3), are also at different points. The distance between the
centers is represented by the center point arrow 88 in FIG. 3.
The shape and size for the cross-sections of the inner 26 and outer
28 circumferential strip elements, as well as for the radial strip
elements, along their lengths, are defined by geometrical circular
techniques which can be readily described in connection with FIGS.
2, 3 and 5.
Before proceeding with this, it should briefly be noted that the
base plane and base level for the diaphragm 12 in FIG. 3, is
represented by the base plane dash-dot line 90. There is then a
short vertically-extending (by reference to the view of FIG. 3)
portion of the diaphragm at 92, and also a short transition portion
at 94 which serves as the transition from the vertical portion to
the onset of the generally spherical shape for the diaphragm.
Now returning to such cross-section shapes and sizes and referring
in more detail to FIG. 3, there is a center relating to the inner
circumferential strip element 26 at each position along the length
of such element. Such center is for an inner circumferential
element circle which serves to define the cross-sectional shape and
size of the element. The center is located a set vertical distance
above the base plane for the diaphragm (represented by the base
plane dash-dot line 90), and a fixed horizontal distance from the
applicable center plane for the diaphragm, represented for the
cross-section of FIG. 3 by the center plane dash-dot line 96. The
vertical distance for the circle center applicable to the
cross-section of FIG. 3 is represented by the vertical inner
circumferential element arrows 100 in FIG. 3; the horizontal
distance is represented by the horizontal inner circumferential
element arrows 102; and the center for the inner circumferential
element circle, in FIG. 3, is at 106.
Now, specifically, the shape and size (the contour of the outer
surface) for the inner circumferential strip element at the
cross-sections along its length, such as the cross-section of FIG.
3, is along a circle from the indicated center having a set radius,
indicated by the radial arrow 108 for the inner circumferential
element circle, as shown in FIG. 3. The base width for the element
is then determined by the intersection of the indicated circle with
the upper surfaces of the adjacent unraised sectors of the
diaphragm. (The base width, thus, of course, is defined analogously
to the base width for the radial strip elements as discussed in
connection with FIG. 5.) As indicated here and in the drawings, the
cross-section shape and size does not vary along this strip element
(except at intersections with the radial strip elements where the
defined cross-sections for the intersecting strips in effect merge
together).
The determination of the shape and size for the outer
circumferential strip element 28 is analogous to that for the inner
circumferential strip element, as just explained. Of course, the
horizontal and vertical distances for the applicable circle will
differ; also, the radius for the applicable circle may differ.
Referring to the cross-section of FIG. 3, the horizontal distance
for the outer circumferential circle center is indicated by the
horizontal outer circumferential element arrows 110; the vertical
distance is indicated by the vertical outer circumferential element
arrows 112; the center for the outer circumferential element circle
is at 114; and the radius for the circle is indicated by the radial
arrow for the outer circumferential circle at 116.
Now referring to the radial strip elements, their shape and size at
various positions along their lengths is determined in a somewhat
related, but different fashion.
With respect to the radial strip elements, the cross-sectional
shape and size (along the outer surface of the element) also is
determined by a circle drawn about a center and by where that
circle joins the unraised sector level. The radius for the circle
is independent of the position. Thus, by reference to the radial
element circle center 118 of FIG. 3, one can see this radius
indicated by the radial arrow 120 for the radial element circle. As
just noted, such radius (its length) remains the same at the
various positions moving down a radial strip element. However, the
center position for such radius, at the various positions, is
determined in a particular way which is apparent by reference to
FIG. 3.
Specifically, such center, at a given position, is the distance
below the radial element rise level spherical envelope, along the
radius for such envelope, which is equal to the radius for the
radial strip element circle. For example, in FIG. 3, the
cross-section for the "north" radial strip element 56 is shown at
the apex of the diaphragm, for purposes of clarity as if the other
radial elements did not merge with such cross-section at the apex.
Thus, at that point, the center for the circle is determined by
moving the radial arrow 82 for the radial element rise level
spherical surface to the apex and by moving downward from the tip
of such arrow a distance equal to the radial arrow 120 for the
radial element circle--i.e., to the radial element circle center
118 of FIG. 3. Similarly, at a position much further down along the
north radial strip element 56, the position of FIG. 5, the center
for the applicable radial element circle, shown at 124, is
similarly determined. Specifically, the arrow 82 for the radial
element rise level spherical surface is rotated to that position,
and the center is determined by moving downward from the tip of
that arrow, along the arrow, a distance equal to the radial arrow
126 for the radial strip element circle at that point--i.e., the
very same distance as at the apex, as represented in and just
explained with reference to FIG. 3. Thus, as indicated, the length
of the radial arrow 126, at the lower level of FIG. 5, is the same
as the comparable radial arrow 120 shown at the apex in FIG. 3.
Of course, as previously explained, the rise level does change
along the radial strip element and the base width also changes,
both decreasing toward the outer edge of the diaphragm. Such
decrease in rise level and decrease in base width, are, of course,
defined by the geometric factors which have been explained and, in
this connection, are well evident in the drawings.
The cross-section shape and size along the cross-strip elements 30
is substantially uniform, as illustrated in FIG. 4 (except at
intersections with one another where the cross-sections for such
strips effectively merge together). Such shape and size is
determined by a circle (to the outer surface of the element)
centered essentially at the level of the surrounding unraised
sectors of the diaphragm. Thus, by reference to FIG. 4, a
cross-element circle center is shown at 128 and a radial arrow 130
for the center and associated circle is shown.
The diaphragm 12 (together with the integral suspension 14 and
skirt 16) are advantageously and conveniently made of 0.001 inch
(0.02540 millimeter) thick titanium. Such thickness is advantageous
and convenient with respect to the competing goals of strength and
lightness. For a size applicable to a voice coil of about 1 inch
(2.540 centimeters) in diameter, the integral structure is
particularly adapted for cold-forming in a die. The structure,
also, is particularly adapted for that size range, and the
following is a list of various specific pertinent dimensional
information for an embodiment of the indicated size range:
______________________________________ the radius for the unraised
0.920 inch (2.337 cm) sector spherical surface envelope the radius
for the radial 0.8694 inch (2.208 cm) element rise level spherical
surface envelope the distance between the two 0.0607 inch (1.542
mm) centers for such spherical surface envelopes the radius for the
radial 0.015 inch (0.381 mm) element circle the radius for the
inner 0.0165 inch (0.419 mm) circumferential element circle the
radius for the outer 0.0165 inch (0.419 mm) circumferential element
circle "vertical" position (above base 0.1345 inch (3.416 mm)
plane) of center for inner circumferential element circle
"horizontal" position (from 0.1875 inch (4.763 mm) center plane) of
center for inner circumferential element circle "vertical" position
(above 0.0705 inch (1.791 mm) base plane) of center for outer
circumferential element circle "horizontal" position (from 0.375
inch (9.525 mm) center plane) of center for outer circumferential
element circle diameter for base of 1.005 inch (2.553 cm) diaphragm
- i.e., for circular base at base plane where dia- phragm and
suspension meet (represented by base diameter arrows 134 in FIG. 3)
comparable diameter to that 0.9840 inch (2.499 cm) immediately
above, but measured above the base plane at the onset of the short
transition portion leading into the short vertical portion near the
outer edge of the diaphragm (represented by the diameter dimension
at transition onset arrows 136 in FIG. 3) diameter dimension for
the 1.900 inches (4.826 cm) total structure - i.e., to outer edge
of skirt (represented by the overall diameter dimension arrows 140
in FIG. 3) diameter dimension to outer 1.370 inches (3.480 cm) edge
of suspension (represented by the outer suspension diameter arrows
142 in FIG. 3) diameter dimension to middle 1.200 inches (3.048 cm)
of suspension (repre- sented by the mid- suspension diameter arrows
144 in FIG. 3) height of skirt above base 0.015 inch (0.381 mm)
plane (represented by the skirt height arrows 146 in FIG. 3) height
of raised pattern above 0.1736 inch (4.409 mm) base plane at apex
(repre- sented by the apex raised pattern arrows 148 in FIG. 3)
unraised sector height above 0.1636 inch (4.155 mm) base plane
applicable at apex (represented by the apex unraised sector arrows
150 in FIG. 3) height for short vertical 0.021 inch (.533 mm)
portion and short transi- tion portion of diaphragm above base
plane (repre- sented by the vertical and transition portion arrows
152 in FIG. 3) height above base plane for radial 0.1586 inch
(4.028 mm) element cross-section circle at apex (represented by the
radial element apex cross- section circle arrows 154 in FIG. 3)
______________________________________
The diaphragm, as described in detail herein, for use as a direct
radiator--i.e., a radiator providing waves which directly emanate
into the surrounding space--is adapted for what is generally
considered the upper audio range--from about 5 kilohertz to 20
kilohertz. For use as a compression driver--i.e., to send sound
waves against a close facing surface and compress the waves between
the surface and diaphragm before they emanate into the surrounding
space--it is adapted to have a range from about 2 to 3 kilohertz to
20 kilohertz. Thus, the diaphragm is adapted to well satisfy the
needs of high frequency speakers--i.e., "tweeters", generally
considered to cover the range from about 5 kilohertz through 20
kilohertz.
By way of example, a variation on the design described in detail
herein, not considered to be as favorable as such design, well
satisfies the characteristics just noted. Such variation has eight
radial strip elements (which are thus 45.degree. apart) with the
concomitant lesser number of, but larger, unraised sector
divisions. Further, such variation does not incorporate the
desirable lowering of the rise level for the radial strip elements
in the direction from the apex toward the outer edge of the
diaphragm, nor the decrease in the base width for such strip
elements in that direction. Thus, according to that form, the
centers for the unraised sector spherical surface envelope and for
the radial element rise level spherical surface envelope are at the
same point. Thus, a uniform separation for such envelopes, then,
resides solely in the difference in the lengths of their radii of,
e.g., in the range of 0.015 inch (0.381 mm). In this connection,
roll-off does not occur in any form raising a concern below the 20
kilohertz upper audio frequency limit and "chirping", which might
typically be expected to begin to arise at about the 5 to 7
kilohertz range for smooth dome-shaped metallic diaphragms of
comparable size, also does not appear to be present in any form
raising practical concern.
The approach and form described herein is considered to be
particularly applicable to diaphragms which are smaller than low
frequency diaphragms. In the form of domes, such low frequency
diaphragms generally have base diameters of in the general ranqe of
12 to 30 inches (30.5 to 76.2 cm). In the form of cones, the same
range generally applies, for the diameter of the base of the cone
or of the larger base of the cone where the apex of the cone is cut
off (usually measured to the outer surface when the thickness of
the diaphragm is significant).
Mid-range diaphragms typically are considered to have such base
diameters, in the range of about 5 to 10 inches (12.7 cm to 25.4
cm). Similarly, the high frequency diaphragms generally have such
base diameters, in the range of about 4 to 5 inches (10.2 cm to
12.7 cm) or less.
In adapting the approach as described herein to a larger high
frequency diaphragm, by way of example, a dome-shaped diaphragm
having approximately a 4-inch (10.2 cm) base diameter, a number of
considerations are apparent.
First, by way of further background, the radius for the general
spherical shape for such a diaphragm might typically be in the
range of about 3 inches (37.6 cm), and the height from the base to
the top might typically be in the range of about 0.7 inch (1.8
cm).
Second, in keeping with the 2-to-1 ratio of radial strip elements
to pyramid-like elements for the particular form of suspension, a
choice of thirty-six radial strip elements might typically be
expected for the "4-inch" size.
Third, to increase stiffness, a rise level for the radial strip
elements (at the apex) of in the range of three times that for the
size described in detail herein--i.e., of about 0.045 to 0.50 inch
(1.1 cm to 1.3 cm) might be typical. However, with such larger
size, radial elements which initially rise with straight sides and
form the circular cross-sectional shape on top of such sides could
be advantageous and convenient. Similarly, the height for the
cross-elements might typically be in the range of three times as
great--i.e., in the range of about 0.015 inches (0.381 mm) with,
however, the straight walls topped by a circular cross-sectional
shape perhaps also advantageous and convenient here.
Because a larger number of radial strip elements and of
cross-elements would apply to the larger size, increased base
widths typically might well not be called for. Similarly, to follow
the same basic configuration, additional circumferential strip
elements would be called for. However, additional height and/or
width for such elements may not necessarily be desirable, with the
role of such elements being to provide anchor or cross-points for
the radial strip elements and cross-strip elements more than to
contribute to stiffness.
As a final matter, it will be apparent to those skilled in the art
that a variety of changes and modifications in the diaphragm device
form, as described in detail herein, may be adopted without
departing from the spirit or scope of the invention.
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